LinkedIn CEO Jeff Weiner wonders where everybody will get the free time to use Google+

Weiner shared the stage with super-agent Ari Emanuel and AllThingsD's Kara Swisher at a Churchill Club event this evening.

Swisher asked if there was a limit to the number of social networks that could coexist, and while Weiner acknowledged that Google had to get more social, he questioned how far it would get.

"Nobody has any free time," he said. "Unlike social platforms and TV, which can coexist, you don't see people using Twitter while they're using Facebook, or using Facebook while they're using LinkedIn."

He went on to say that the social networking landscape was pretty understandable before -- people generally use LinkedIn for your professional life, Facebook for family and friends, and Twitter to microcast your thoughts to an audience. But, "you introduce google+, where am I going to spend that next minute or hour of my discretionary time? I have no more time."

It's a good point -- while Google+ has grown fast in its first couple of weeks, at some point social networking becomes a zero sum game. For Google+ to win in the mainstream, somebody else is going to have to lose.

Emanuel proposed that all these social networks would eventually need original content to differentiate himself, which is where the Hollywood talent agents like him come in. "Fuckin' a, with leverage," as he put it.